NEW YORK (Reuters) - Citigroup Inc Chief Executive Michael Corbat named Jane Fraser as the new head of the bank's mortgage business on Monday ,as current CitiMortgage CEO Sanjiv Das plans to leave the bank to pursue other opportunities, according to an internal memo.

Das took over Citigroup's mortgage business at the height of the financial crisis in 2008 as it was losing billions of dollars on bad subprime housing bets. He will remain at the bank for a few months to assist on mortgage issues related to the government, according to the memo.

Fraser has been CEO of Citi's private bank for the past four years. Mark Mason, who is a senior executive at Citi Holdings, will take over that role.

Francesco Vanni d'Archirafi, who now leads Citigroup's transaction services business, will take over as CEO of Citi Holdings, the division that holds all noncore assets that Citi is winding down or selling.